sexta-feira, 21 de janeiro de 2011

The impact of the Andes

The rise of the Andes not only reversed the course of rivers that cut through the Amazon today, but created the environment for the diversification of species that make the region become one of the most biodiverse in the world. Of course this was not the only factor driving the variety of flora and fauna of the region. There were ice ages, the most recent changes in relief, but to researchers who published the article, geological history can make a major contribution to understanding the Amazon today.

There are up to 10 million years, the Amazon was much more extensive, stretching from northern Parana to Colombia. In the rivers that flowed into the Pacific and also in those who had already found the path to the east toward the Atlantic, live catfish, piranhas and discus. There was a diverse mammal fauna that included rodents, marsupials and sloths and ancestors of hoofed animals. Farther south, were also found turtles and plants that possibly came from the south, the reverse link that existed between South America and Australia and Antarctica.

The Andes began to rise past 23 million years, causing the first major diversification of modern plants and animals. But the mountains still continue to increase to close the Isthmus of Panama 3.5 million years ago, causing over this long period new peaks of biological diversification.

The ancient fauna in the estuaries, representative of marine environments, has been replaced. A large area of ponds and plants emerged in Western Amazonia, which was colonized by mollusks and oysters. Ali had also gavials, alligators and turtles. The largest alligator ever known, Purussaurus, which reached 12 feet long, lived during this period in this swampy region. The rainforest was fragmented, but it resembled the current Amazonian vegetation.

Over time, the region turned into an environment similar to the Pantanal, which was called Acre. The plains were dominated by grass alagação and inhabited by a variety of sloths and anteaters. Most mollusks have adapted to this environment inland, but remained turtles, caimans and gharials.

Between 7 and 5 million years ago, the Marshes have been replaced by a forest environment. The western Amazon, then, was already familiar with the geography today. The ancestors of the pink dolphin had swum towards the east, and lived in this region.

After the Andes have already been raised, there are 3.5 million years, changes in the environment continued to occur. Ice ages came and constraints that led to the extinction of megafauna. The relief segiu changing, there was elevation of the land, changes in the patterns of rivers. The link established with the Isthmus of Panama allowed the migration of species from the north. The Andes also fertilize the soil of the Amazon, contributing to the high productivity of the ecosystem. And continuing, as there are millions of years, migration by ocean, with species from North Africa as well.

But the role of biodiversity in the Andes may still be recognized. Currently, an area of approximately 1 million square kilometers in the western Amazon, where he was once a large swamp, has the biggest biodiversity of the entire Amazon. In this region, as amended by the Andes, the variety of plants and animals much larger than in other older areas of the Amazon. (Vandré Fonseca)